(1) Field of the Invention
This invention relates to a display device, which displays road traffic information along the displayed roads.
(2) Description of the Related Art
Recently, a navigation device as a system for supporting the driving is widely used for a driver of a mobile unit to reach his or her destination. In this device, a GPS receiver mounted on the mobile unit receives GPS information sent from a plurality of GPS satellites, then a present position of the mobile unit is computed on the basis of the received information and then, on the basis of the computed position, a mark indicating the present position of the mobile unit can be displayed on a map, which is displayed on a displaying section disposed in the mobile unit.
Further, in this navigation device, besides that the present position of the mobile unit is displayed as the mark, various traffic information such as traffic congestion, traffic accident and traffic regulation provided from the outside of the mobile unit is received and displayed on the displaying section, thereby further supporting the driver.
A vehicle information communication system (VICS) of the Vehicle Information Communication System Center Incorporated Foundation is a typical system for providing traffic information.
When traffic information is displayed on a displaying section of a mobile unit on the basis of the VICS information, one can use three kinds of the displaying forms from the level 1 to the level 3. Particularly, when the level 3 of the displaying form is used, traffic congestion information, traffic regulation information and traffic accident information can be directly displayed on a map, which is displayed in a navigation device.
In the level 3 of the displaying form, arrows indicating traffic congestion information, traffic regulation information and traffic accident information are displayed along roads in the map. A driver can see the position and length of each arrow for the roads in the map, thereby the driver can recognize a position and a section of the traffic congestion, regulation and accident on actual roads.
When one receives traffic information, one may receive a plurality of different traffic informations with respect to the same section of one road. For example, when one receives traffic congestion information and traffic regulation information at the same time with respect to the same section of one road, arrows corresponding to the respective informations are displayed overlapped with each other in the level 3 of the displaying form, therefore one may hardly see one arrow out of the two arrows.
Furthermore, when a plurality of different roads are built above and below, which is often seen in a relation between an ordinary way and an expressway, an arrow indicating traffic information of one road and an arrow indicating traffic information of another road are displayed overlapped with each other, therefore one may hardly see one arrow out of the two arrows.
It is therefore an objective of the present invention to solve the above problem and to provide a display device, by which the road traffic information can be easily seen.
In order to attain the above objective, the present invention is to provide a display device, for displaying a map on a displaying section of the display device and also for displaying traffic information along roads in the map on the basis of road traffic information, comprising: a composing section for composing traffic information images having different forms from each other depending upon types of the traffic information; and a superposing section for superposing the traffic information images having different forms from each other so that the traffic information images are alternately displayed on an image of the map.
Preferably, the types of the traffic information consist of traffic information on expressways and traffic information on ordinary ways.
Preferably, the types of the traffic information consist of at least two out of traffic congestion information, traffic regulation information and traffic accident information.
Preferably, the superposing section superposes the traffic information images having different forms from each other so that the traffic information images are alternately displayed in a zone where the traffic information images overlap with each other on the image of the map.
Preferably, the superposing section superposes the traffic information images so that the traffic information image is always displayed in a zone where the traffic information images do not overlap with each other on the image of the map.
Preferably, the composing section composes the traffic information images so that the traffic information images are composed by using different displaying colors depending upon a type of the traffic information or a type of a road.